A flier circulated by Local 1181 of the Amalgamated Transit Union is warning members of the 9,000-strong union to “think twice” before crossing picket lines. “Strikers will be placed on a published scab list and subject to union discipline — possible fines, suspension or expulsion,” it reads.

The warning comes a day after drivers from a non-striking union were jeered for reporting to work at a Staten Island bus depot for the first time since the strike began on Jan. 16.

The work stoppage was launched Jan. 16 after the city removed job protections and seniority rights for workers from new bids covering 1,100 bus routes.

Even managers of school-bus companies that employ Local 1181 workers say they have drivers and matrons who want to return to work, especially with health benefits set to expire tomorrow, but who are concerned about crossing picket lines.

Pioneer Transportation Corp. president Neil Strahl pleaded with union members to negotiate cost savings so current contractors can remain competitive against new companies that aren’t bound by the employee protections.

“If you continue to strike . . . there is a serious chance that your jobs may disappear, either through permanent replacement drivers or companies that replace Pioneer,” Strahl wrote.